He’s been key for us this year, the way he’s played on both ends of the floor.

Down six points in the fourth quarter, the Nets, with a five-game winning streak on the line, were in trouble. Their big man and should-be All-Star, Brook Lopez, had been stifled, so the Nets were deprived of a vital threat. Then came a soft jumper from Lopez, and then another. The Nets were instantly transformed.

Next time down the court, he drew the defense close and kicked the ball out, leaving another scorer, Joe Johnson, open. The Nets were on their way.

What used to be an event around this club — Lopez taking over — is now the norm. His evolution, slow in the making, interrupted by slumps and injury, might be the main reason the Nets have shed their old ways and climbed into a higher tier in the NBA. With a victory at Madison Square Garden on Monday, the Nets had a hot streak, winners of 10 of 12, and sat just one game behind the Knicks for the Atlantic Division lead.

The question that has dogged Lopez — when will he truly emerge? — has been replaced by a new idea: At this moment, at just 24, he might just be the best center in the game.

With an average of 18.6 points a game entering last night’s game in Houston, he is the leading scorer on his team and the highest-scoring center in the league. His rebounds are up, he’s blocking more shots and there is a smartness and aggressiveness to his game that had been missing.

Brooklyn's Brook Lopez blocks the shot of Houston center Omer Asik in the first quarter Saturday night at the Toyota Cente, one of five blocks for the fifth-year center.Brett Davis/USA TODAY Sports

"He’s been key for us this year, the way he’s played on both ends of the floor," said teammate Deron Williams. "We knew what he could do offensively. He can score the ball. But what he’s done defensively — blocking shots, changing shots — has been a huge lift for this team."

If Williams, the star point guard, is the team’s general, and Johnson the sharpshooting specialist, then Lopez is the stalwart. For a player who used to be regarded as soft, Lopez, laid back, from Southern California, now somehow symbolizes the team’s new gritty Atlantic Avenue, Brooklyn, image.

IGNORE THE RUMORS

Only last spring, with Williams urging them on, the Nets were about to sacrifice Lopez to the Orlando Magic for a more glamorous choice — Dwight Howard. The deal collapsed because the Magic did not view Lopez as a worthy replacement.

The Nets switched course, delivering a four-year, $60.8 million contract to Lopez last summer. Even with his emergence, and with Howard laboring in his new home with the Los Angeles Lakers, the possibility has not disappeared. A Feb. 21 trade deadline looms, and if the Lakers think they can’t re-sign Howard, they may look to the Nets for a swap.

"It is what it is," said Lopez with the same measure of resignation he expressed last season. "I’ve dealt with it before."

He is a specimen at 7 feet tall and 265 pounds, and was drafted 10th in the 2008 Draft. But his star was tethered to a stagnant team. In his second year, the Nets lost their first 18 and won only 12 the entire season. And depending on the coach — P.J. Carlesimo is his fourth in five seasons in the NBA — his assignment has shifted.

Avery Johnson, hired in 2010 and fired last month, used Lopez as more of a roaming defender, somewhat like a free safety in football. That meant racing out toward an open shooter, then turning to chase down rebounds. That didn’t always work, and Lopez’s rebounds dropped. He is averaging 7.3 rebounds and 2.1 blocks a game this season, not spectacular but solid complements to his scoring. In player efficiency rating, or PER, an ESPN formula designed to measure a player’s worth against others in the league, Lopez ranks in the top five, alongside LeBron James, Kevin Durant, Chris Paul and Carmelo Anthony and higher than Tim Duncan and Kobe Bryant.

He deflects newfound praise, saying he has benefited from having Williams and Johnson alongside him. He calls himself merely the Nets’ "third option."

"You want to be the best you can be in every area," Lopez said. "You don’t really want to have one glaring thing where you’re just awful at. I just keep trying to improve."

From the first grade, when he started playing in Long Beach, Calif., Lopez shared the court with his identical twin brother, Robin. As two 7-footers playing together, it was only natural for one twin (Brook) to develop into an offensive player and the other (Robin) to focus more on defense.

"I think that developed just intuitively," said Alex Lopez, the twins’ oldest brother in a family of four boys. Their mother, Deborah Ledford, was a 6-foot-tall swimmer at Sanford, and their father, Heriberto Lopez, was a baseball player from Cuba. Another older brother, Chris, is 6-foot-6, and Alex is 6-10.

"Brook was just more of a guy to take charge offensively, and Robin knew he could quietly lead the defense. And this goes back to their rec games," Alex said.

Growing up, Brook and Alex shared bunk beds. They were McDonald’s All-Americans at Fresno’s San Joaquin Memorial High School (where Brook acted in the school musicals "West Side Story’’ and "Footloose’’) and went to Stanford together (where Robin dated golfer Michelle Wie his sophomore year). They both turned pro after their sophomore year. Robin went to Phoenix, playing behind Shaquille O’Neal before landing in New Orleans, where he is now the Hornets’ starting center.

In some ways, Brook is a throwback, able to receive the ball in the low post near the basket and create a play from nothing. O’Neal calls Brook and Philadelphia’s Andrew Bynum the only true centers left in the NBA.

"He plays like a real big man," O’Neal told The Star-Ledger. "I don’t mind big men doing pick-and-roll some of the time, but he didn’t make his name only doing that."

O’Neal said he prefers Brook’s game to Howard’s, regarding him as a young Tim Duncan.

Brook breaking his foot in the final preseason game limited him to all of five games last season and no doubt complicated the Nets’ pursuit of Howard.

With Howard on a deflated Lakers team, the two players’ circumstances have practically reversed.

Still, Billy King, the Nets’ general manager, made a point recently of reassuring Brook.

"I just went to him and said, ‘Brook, don’t fall for it. Don’t buy into it,’ " King said. "I said, ‘We’re not talking to L.A., so don’t get distracted by all that nonsense.’ "

Throughout the Howard saga, Brook has remained steadfast to the Nets, even passing up the chance to sign an offer sheet from another team last summer. He knew, he said, "I’d be an important piece in what they’re trying to do here."

His stardom may have been delayed, but, Brook said, dispensing modesty for just a moment, "I never questioned myself."